Is screening for prostate cancer worthwhile?
Two major studies published simultaneously, in the New England Journal of Medicine, on the effectiveness of screening for prostate cancer have produced conflicting results.
In the European study, PSA-based screening reduced the rate of death from prostate cancer by 20% but was associated with a high risk of overdiagnosis. In the US study, the mortality rate did not differ significantly between the screening and control groups.
The European Randomized Study of Screening for Prostate Cancer (ERSPC), started in the early 1990s and reported on 162,000 men aged 55-69, from eight countries. The men were randomly assigned to a group that was offered PSA screening at an average of once every 4 years or to a control group who were not screened.
Uptake of screening was good, with 82% of men accepting at least one offer of a PSA test. During the median follow up of 9 years the cumulative incidence of prostate cancer was 8.2% in the screening group versus 4.8% in the control group. The absolute risk difference for death was 0.71 fewer deaths per 1,000 men in the screening arm. The study authors calculated therefore that 1,410 men would need to be screened and 48 additional cases of prostate cancer would need to be treated to prevent one death from prostate cancer.
The Prostate, Lung, Colorectal and Ovarian Cancer Screening Trial (PLCO) began in 1993 and randomised almost 77,000 men to receive either annual screening or ‘usual care' as a control. Men in the screening group were offered annual PSA testing for 6 years and digital rectal examination for 4 years. Importantly, ‘usual care' sometimes included screening, as some insurance organisations in the US already provide this.
Similar rates of uptake for PSA testing to the European study were seen (approximately 85%). After 7 years of follow up, the cumulative incidence of prostate cancer was 7.35% in the screening group versus 6.05% in the control group. A total of 50 prostate cancer deaths were seen in the screening group compared with 44 in the control group – this reflects low death rates of 2 and 1.7 per 10,000 person-years in each arm, with no statistically significant difference in death rates between the two arms of the study.
The results from the European study are likely to be more closely applicable to the UK. Significant amounts of screening, both formally and informally, diluted the difference in incidence of prostate cancer between the two arms of the American study, whereas the control group in the European study more closely resembles current UK practice.
The European Association of Urology has, unsurprisingly, adopted the conclusions of the ERSPC study, and in a position statement concluded ‘current published data are insufficient to recommend the adoption of population screening for prostate cancer … due to the large overtreatment effect' and that ‘before screening is considered by national health authorities, the level of current opportunistic screening, overdiagnosis, overtreatment, quality of life, costs and cost-effectiveness should be taken into account'.
So where does this leave us? The CMO concluded that GPs should continue to follow the guidance contained within the Prostate Cancer Risk Management Programme (PCRMP) guidelines, with men entitled to receive a PSA test provided an ‘informed' choice has been made. The decision aid materials contained in the PRCMP will be updated to reflect the findings of these studies, and the DH has asked the UK National Screening Committee to review the evidence and make recommendations.
However, the data from the ERSPC would suggest that although a screening programme could save lives, this would be at enormous cost both to overdiagnosed and overtreated individual patients, and to the health service as a whole. It seems unlikely that a national screening programme will materialise until a better screening test than PSA is developed.
• Schroder FH, Hugosson J, Roobol MJ et al. Screening and Prostate Cancer Mortality in a Randomized European Study. N Engl J Med 2009;3601320-8
• Andriole GL, Grubb RL, Buys SS et al. Mortality Results from a Randomized Prostate Cancer Screening Trial. N Eng J Med 2009;360:1310-9
Dr Jonathan Rees
GPwSI Urology, Bristol